SAT Subject Test Chemistry,10 edition

Now check   the formal  charges:

The P   has a   formal  charge  of  +1  and the O   has a   formal  charge  of  –1. These   can be

eliminated  by  moving  a   pair    of  electrons   around  from    the O   into    a   second  bond:

Both    aluminum    chloride    and sodium  phosphate   are ionic.

AlCl 3 :

C.

D. Na 3 PO 4

9 . Be  and B,  because they    can join    to  only    two or  three   hydrogens,  respectively,   since   they    have

fewer   than    four    valence electrons.  The elements    Mg  and Al  may also    do  this,   as  could   Na, Ca,

and the other   active  metals  of  Groups  I   and II.

10 . E
A. NH 3 is polar (positive end at base of pyramid, negative end at N).

B. NO 2     and ClO 2   are both    angular molecules,  therefore   polar.